Proceedings of the PowerSkin Conference

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Delft University of Technology

Proceedings of the PowerSkin Conference

January 19th 2017, Munich

Auer, Thomas; Knaack, Ulrich; Schneider, Jens

Publication date

2017

Document Version

Final published version

Citation (APA)

Auer, T., Knaack, U., & Schneider, J. (Eds.) (2017). Proceedings of the PowerSkin Conference: January

19th 2017, Munich. TU Delft Open.

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This work is downloaded from Delft University of Technology.

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JANUARY 19

TH

2017 – MUNICH

POWERSKIN

CONFERENCE

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JANUARY 19

TH

2017 – MUNICH

POWERSKIN

CONFERENCE

PROCEEDINGS

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JANUARY 19TH_{2017 – MUNICH}

POWERSKIN CONFERENCE

The Building Skin has evolved enormously over the past decades. Energy performance and environmental quality of buildings are significantly determined by the building envelope. The façade has experienced a change in its role as an adaptive climate control system that leverages the synergies between form, material, mechanical and energy systems in an integrated design.

The PowerSkin Conference aims to address the role of building skins to accomplish a carbon neutral building stock. Topics such as building operation, embodied energy, energy generation and storage in context of façades, structure and environment are considered.

Three main themes will be showcased in presentations of recent scientific research and developments as well as projects related to building skins from the perspectives of material, technology and design: Environment – Façades or elements of façades which aim for the provision of highly comfortable surroundings where environmental control strategies as well as energy generation and/or storage are integral part of an active skin.

Façade Design – The building envelope as an interface for the interaction between indoor and outdoor environment. This topic is focused on function and energy performance, technical development and material properties.

Façade Engineering – New concepts, accomplished projects, and visions for the interaction between building structure, envelope and energy technologies.

TU München, Prof. Dipl.-Ing. Thomas Auer, TU Darmstadt,

Prof. Dr. Ing. Jens Schneider and TU Delft, Prof. Dr.-Ing. Ulrich Knaack are organizing the PowerSkin Conference in collaboration with BAU 2017. It is the first event of a biennial series. On January 19th_{, 2017}

architects, engineers and scientists present their latest developments and research projects for public discussion.

Publisher

TU Delft Open

TU Delft / Faculty of Architecture and the Built Environment Julianalaan 134, 2628 BL Delft, The Netherlands

Editors

Thomas Auer Ulrich Knaack Jens Schneider

Editorial office

TU Darmstadt – Miriam Schuster (MSc) TU München – Uta Stettner

Design & layout

Design – Sirene Ontwerpers, Rotterdam Layout – Phoebus Panigyrakis, TU Delft

Cover image

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003 JANUARY 19TH_{2017 – MUNICH}_{POWERSKIN CONFERENCE | PROCEEDINGS} Contents

Preface

011

KEYNOTES

015

ENVIRONMENT

017

Designing façades for carbon neutral buildings

Winfried Heusler

027

Building Envelope as Heat Generator –

The impact of Water-filled ETFE Cushion on Energy saving and Comfort

Abolfazl Ganji Kheybari, Jochen Lam

039

Anaerobic domestic waste water treatment coupled to a bioreactor

facade for the production of biogas, heat and biomass*

Martin Kerner

049

Free-Form 2.0 –

Building prefabricated segmented concrete free-form Shells

Alexander Stahr, Martin Dembski, Michael Theuer, Lars Janke

061

Machine code functions in BIM for cost-effective high-quality buildings

Christoph Maurer, Wendelin Sprenger, Steffen Franz, Jan Lodewijks, Uwe Rüppel, Tilmann E. Kuhn

071

Thermal and Energy Performance of Double Skin Facades

in Different Climate Types

Ajla Aksamija

083

How Material Performance of Building Façade Affect Urban Microclimate

Ata Chokhachian, Katia Perini, Mark Sen Dong, Thomas Auer

097

An investigation on the relation between outdoor comfort and

people’s mobility – The Elytra Filament Pavilion survey

Daniele Santucci, Eduard Mildenberger, Boris Plotnikov

109

Updated urban facade design for quieter outdoor spaces*

Jochen Krimm, Holger Techen, Ulrich Knaack

111

Optimised Parametric Model of a Modular Multifunctional Climate

Adaptive Façade for Shopping Centres Retrofitting*

Riccardo Pinotti, Stefano Avesani, Annamaria Belleri, Giuseppe De Michele, Philip Ingenhoven

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Contents

113

Field monitoring in Mediterranean climate to quantify

thermal performances of vertical greening systems

Katia Perini, Francesca Bazzocchi

123

Benefit E2 – Building integrated solar active strategies

Christoph Kuhn, Steffen Wurzbacher, Christoph Drebes

133

FAÇADE DESIGN

135

Research and Development of Innovative Materials at the

Convergence of Art, Architecture and New Technologies

Heike Klussmann, Thorsten Klooster

147

Retrofit of a “Brutalist” office building from the ‘70s in Rome

Alberto Raimondi

159

Variable Façade – Method to apply a dynamic façade solution in Santiago, Chile

Claudio Vásquez, Renato D’Alençon

171

Integration of technology components in cladding systems

Philipp Molter, Tina Wolf, Michael Reifer, Thomas Auer

179

Multi-active façade for Swedish multi-family homes renovation:

Evaluating the potentials of passive design measures*

Susanne Gosztonyi, Magdalena Stefanowicz, Ricardo Bernardo, Åke Blomsterberg

181

Light-transmitting energy-harvesting systems – Review of selected case-studies

Marcin Brzezicki

191

Silicones enabling crystal clear connections

Valérie Hayez, Dominique Culot, Markus Plettau

201

GFRP Reinforcement and Anchorage Concepts for filigree

Energy-Efficient Façades made of UHPC

Milan Schultz-Cornelius, Matthias Pahn

213

Thermal optimization of curtain wall façade by

application of aerogel technology*

David Appelfeld

215

Fixed sunshade device for overhead glazing

Daniel Kleineher

227

Subdivided switchable sun protection glazing**

Marzena Husser, Walter Haase, Werner Sobek

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Contents

229

FAÇADE ENGINEERING

231

A zero-energy refurbishment solution for residential apartment

buildings by applying an integrated, prefabricated façade module

Thaleia Konstantinou, Olivia Guerra-Santin, Juan Azcarate-Aguerre, Tillmann Klein, Sacha Silvester

241

Timber Prototype – High Performance Solid Timber Constructions

Hans Drexler, Oliver Bucklin, Angela Rohr, Oliver David Krieg, Achim Menges

253

Powerskin – Fully Fashioned*

Claudia Lüling, Iva Richter

255

Solar Concentrating Façade

Sidi Mohamed Ezzahiri, Badia S. Nasif, Jan Krieg, Anco Bakker, Carlos Infante Ferreira

267

Viability study of Solar Chimneys in Germany – Analysis and Building Simulation

Lukas Schwan, Eabi Kiluthattil, Madjid Madjidi, Thomas Auer

279

Hybridization of solar thermal systems into architectural envelopes

Beñat Arregi, Roberto Garay, Peru Elguezabal

289

Solar façades – Main barriers for widespread façade

integration of solar technologies*

Alejandro Prieto, Ulrich Knaack, Thomas Auer, Tillmann Klein

291

Solar PV Building Skins – Structural Requirements and Environmental Benefits*

Claudia Hemmerle

293

Infra-Lightweight Concrete – A monolithic building skin

Mike Schlaich, Alex Hückler, Claudia Lösch

305

Cellular Lattice-Based Envelopes with Additive Manufacturing*

Roberto Naboni, Anja Kunic, Luca Breseghello, Ingrid Paoletti

307

3d-Printed Low-tech Future Façades –

Development of 3d-printed Functional-Geometries for Building Envelopes

Moritz Mungenast

319

Convective Concrete –

Additive Manufacturing to facilitate activation of thermal mass*

Dennis de Witte, Marie L. de Klijn-Chevalerias, Roel C.G.M. Loonen, Jan L.M. Hensen, Ulrich Knaack, Gregor Zimmermann

*

Full paper published in JFDE / Journal of Façade Design and Engineering, Volume 5, Number 1, 2017.

**

Full paper published in GS&E / Glass structures & Engineering, 2017.

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Preface

The “third skin” of human beings – the building envelope – has a

long history of development with a major impact on architecture.

As an interface between inside and outside, facades not only

determine aspects such as performance and energy efficiency, they

also determine the aesthetics of buildings and cities; to the extend

that they can create cultural identity. The invention of the curtain

wall made facades independent from the building structure, but it

remained an important – yet passive – element.

In the past 2 decades, the building envelope has experienced a change in its role as an adaptive climate control system that leverages the synergies between form, light, material, energy and mechanical systems in an integrated manner. Contemporary façade design aims for an optimized environmental quality while minimizing the use of resources. Indoor environmental quality and operational energy performance were a main focus in the 1990s, whereas in the next decade, design and research also put more and more consideration into outdoor environmental quality. Current research is focusing on materiality in the context of building life cycle, design integration and maintenance. Sustainable, smart materials – providing an auto-reactive, passive environmental control mechanism – as well as active systems for environmental control, along with energy generation and storage became areas for both R&D and construction practice.

Over the past decades, glass developed into the dominating cladding material due to its improved thermal performance and adaptability with regard to transparency, solar and daylight control. This allows a flexible interaction between the indoor and outdoor environment and offers the potential of a dynamic control strategy. Recent developments provide an integration of mechanical climate control systems – such as decentralized mechanical ventilation – and components for energy generation and storage.

On the one hand, this could lead to a building design that is fully independent of local climate conditions, building culture, and other contextual aspects, while still providing an optimized environmental quality. On the other hand, it also enables architects and engineers to design buildings that interact with and adapt to climate conditions and user demands as well as respect local conditions and local context. Such a design approach provides the opportunity to bring the local identity back into the architectural language.

The PowerSkin Conference and the proceedings address three main topics: Façade, Structure and Environment. The presentations and papers showcase recent scientific research and developments, along with projects related to building skin from the perspectives of material, technological and design.

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Preface

We would like to express our thanks and appreciation to our peers and colleagues, willing to participate in the intensive process of reviewing abstracts and papers – supporting the experienced conference participants to further develop and improve. Special thanks to Prof. Dr. Anne Beim / KADK Copenhagen; Paul Carew / PJC Consulting Cape Town; Prof. Dr.-Ing. Tillmann Klein / TU Delft and TU München; Prof. Dr. Stephen Selkowitz, Lawrence Berkley National Lab (LBNL); Prof. Dr.-Ing. Frank Wellershoff / HafenCity University Hamburg. Also we would like to thank Thaleia Konstantinou / TU Delft; Phoebus Ilias Panigyrakis / TU Delft; Véro Crickx / Rotterdam and Frank van der Hoven / TU Delft for their support with the journal and the conference proceeding.

And finally: our biggest thank you goes to Uta Stettner / TU München and Miriam Schuster / TU Darmstadt – they were the engine pushing the development process and the

conference itself. Great work!

Thomas Auer Ulrich Knaack Jens Schneider

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Preface

Prof. Dipl.-Ing. Thomas Auer

Trained as a Process Engineer at the Technical University in Stuttgart, Thomas is a partner and managing director of Transsolar GmbH, a German engineering firm specialized in energy efficient building design and environmental quality with offices in Stuttgart, Munich, Paris and New York. In January of 2014 Thomas became Professor for building technology and climate responsive design at the TU Munich.

Thomas collaborated with world known architecture firms on numerous international design projects and competitions. A specialist in the fields of integrated building systems and energy efficiency in buildings as well as sustainable urban design, Thomas has developed concepts for projects around the world noted for their innovative design and energy performance – an integral part of signature architecture. The office tower for Manitoba Hydro in downtown Winnipeg, Canada – is considered one of the most energy efficient high-rise buildings in North America. Lower Don lands, Toronto – is going to be among the first carbon neutral districts in North America.

Outside of Transsolar, Thomas taught at Yale University and was a visiting professor at the ESA in Paris and other Universities. He speaks frequently at conferences and symposia. In 2010 Thomas received the Treehugger “best of green” award as “best engineer”.

Prof. Dr.-Ing. Ulrich Knaack

Prof. Dr.-Ing. Ulrich Knaack (1964) was trained as an architect at the RWTH Aachen / Germany. After earning his degree he worked at the university as researcher in the field of structural use of glass and completed his studies with a PhD.

In his professional career Knaack worked as architect and general planner in Düsseldorf / Germany, succeeding in national and international competitions. His projects include high-rise and office buildings, commercial buildings and stadiums. In his academic career Knaack was professor for Design and Construction at the Hochschule OWL / Germany. He also was and still is appointed professor for Design of Construction at the Delft University of Technology / Faculty of Architecture, Netherlands where he developed the Façade Research Group. In parallel he is professor for Façade Technology at the TU Darmstadt / Faculty of Civil engineering/ Germany where he participates in the Institute of Structural Mechanics and Design.

He organizes interdisciplinary design workshops and symposiums in the field of façades and is author of several well-known reference books, articles and lectures.

Prof. Dr.-Ing. Jens Schneider

Prof. Dr.-Ing. Jens Schneider (1969) is a full professor for structural engineering at the Institute of Structural Mechanics and Design, TU Darmstadt (Germany). After his studies in civil engineering in Darmstadt and Coimbra (Portugal), he received his PhD from TU Darmstadt in 2001 in a topic about structural glass design.

From 2001-2005 he worked at the engineering office Schlaich, Bergermann and Partner, where he was involved in the structural design of complex steel, glass and concrete structures. In 2006 he was appointed as an authorized sworn expert on glass structures, in 2007 to the position of a professor for structural engineering in Frankfurt and in 2009 to his current position at TU Darmstadt. Since 2011, he is also partner in his engineering office SGS GmbH in Heusenstamm / Frankfurt. Since 2015, he leads the European project group for the preparation of the new Eurocode 11 „Structural Glass“. He is specialized in structural mechanics of glass & polymers, façade structures, structural design and synergetic, energy-efficient design of façades and buildings.

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Preface

SCIENTIFIC COMMITTEE

Prof. Dipl.-Ing. Thomas Auer Prof. Dr.-Ing. Ulrich Knaack

Prof. Dr. Anne Beim Prof. Dr.-Ing. Jens Schneider

Paul Carew, B.Eng. Prof. Dr. Stephen Selkowitz

Prof. Dr.-Ing. Tillmann Klein Prof. Dr.-Ing. Frank Wellershoff

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Keynotes

KEYNOTES

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Achim Menges

INSTITUTE PROFILE

The Institute for Computational Design (ICD) at the University of Stuttgart was founded in 2008. It is dedicated to the teaching and research of computational design and computer-aided manufacturing processes in architecture. The ICD has received international recognition as particularly innovative research setting and has garnered considerable research funds.

The ICD’s goal is to prepare students for the continuing advancement of computational processes in architecture, as they merge the fields of design, engineering, planning and construction. The interrelation of such topics is exposed as both a technical and intellectual venture of formal, spatial, constructional and ecological potentials.

There are two primary research fields at the ICD: the theoretical and practical development of generative computational design processes, and the integral use of computer-controlled manufacturing processes with a particular focus on robotic fabrication. These topics are examined through the development, specifically, of computational methods which balance the reciprocities of form, material, structure, and environment, and integrate technological advancements in manufacturing for the production of performative material and building systems. The LBNL Windows/Daylighting/Façade team has been exploring these challenges for 40 years, collaborating with researchers, manufacturers, design teams, and building owners globally to move viable solutions into practice. Much of this body of work can be reviewed at http://facades.lbl.gov and over 300 publications can be downloaded from http://eta.lbl.gov/publications

Achim Menges is a registered architect and professor at the University of Stuttgart, where he is the founding director of the Institute for Computational Design at the University of Stuttgart. In addition, he currently also is Visiting Professor in Architecture at Harvard University’s Graduate School of Design. He graduated with honours from the AA School of Architecture in London, where he subsequently taught as Unit and Studio Master in the AA Diploma School and AA Graduate School.

Achim Menges practice and research focuses on the development of integrative design processes at the intersection of design computation, biomimetic engineering and robotic manufacturing that enables a performative and sustainable built environment. His institute is an integral part of the DFG Collaborative Research Centre SFB-TRR 141 “Biological Design and Integrative Structures” and the DFG Collaborative Research Centre SFB 1244 “Adaptive Skins and Structures”. He has published several books on this work and related fields of design research, and he is the author/coauthor of more than 125 scientific papers and numerous articles. His projects and design research has received many international awards, has been published and exhibited worldwide, and form parts of several renowned museum collections.

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Stephen Selkowitz

FUTURE BUILDING SKINS –

SMART, ACTIVE AND ADAPTIVE FAÇADE SOLUTIONS

The building skin alternately connects occupants to the pleasures of the external environment and shelters them from its harshest impacts, using materials, systems and energy to actively manage that relationship. Given the dynamics and extremes of the outdoor environment and the changing personal and functional needs of occupants, successful management requires an active and adaptive building skin that senses and responds to changing needs and requirements. This concept is not new, but it is rarely executed effectively since elegant conceptual designs often run afoul of the realities of the physics of heat and light, the frailties of technology, the challenge of budgets and the behaviour of people, typically defaulting to a static compromise solution that rarely satisfies divergent performance needs. In this presentation we look ahead over a 5 to 15 year time horizon to first define a series of idealized, yet achievable trends and solutions, then identify the technologies, systems, tools and processes we would need to realize them and finally explore how to accelerate some promising high performance glazing, shading and daylighting systems options that will deliver these solutions to a range of building applications and markets.

The LBNL Windows/Daylighting/Façade team has been exploring these challenges for 40 years, collaborating with researchers, manufacturers, design teams, and building owners globally to move viable solutions into practice. Much of this body of work can be reviewed at http://facades.lbl.gov and over 300 publications can be downloaded from http://eta.lbl.gov/publications

Stephen Selkowitz is Senior Advisor for Building Science, Lawrence Berkeley National Laboratory, now in a part-time research and strategic planning role after leading LBNL’s building performance teams in research, development, and deployment of energy efficient technologies and sustainable design practices for 40 years. An internationally recognized expert on window technologies, window software tools, façade systems, shading solutions, daylighting, and integrated building systems solutions he created and then led the LBNL Windows and Daylighting Group until 2015. The LBNL team has been instrumental in partnering with industry to introduce new technologies to building markets, e.g. low-e, spectrally selective and electrochromic coatings, and in creating a suite of tools used by researchers, manufacturers and designers globally, e.g. WINDOW, THERM, Optics, Radiance, Energy Plus. He served as Department Head for the LBNL Building Technologies Department for 25 years, partnering with industry to develop and demonstrate new building technologies, systems, processes and tools. He serves as Scientific Advisor to four building science programs globally that address zero net energy building solutions, is employed as a consultant to industry, has spoken at over 400 scientific, business and industry venues and authored over 170 publications, 4 books and holds 2 patents. He holds an AB in Physics from Harvard College and an MFA in Environmental Design from California Institute of the Arts. In 2012 he was the recipient of the first LBNL Lifetime Achievement Award for Societal Impact and in 2014 won McGraw Hill/ENR’s prestigious Award of Excellence for “relentlessly working to reduce the carbon footprint of buildings and for moving the nation towards better building performance.”

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Environment

ENVIRONMENT

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Designing façades for carbon neutral buildings

Designing façades for

carbon neutral buildings

Winfried Heusler1

1 Schüco International KG, Germany, www.schueco.com; Detmold School of Architecture and Interior Architecture, www.hs-owl.de/fb1

Abstract

Façades are vital not only for the external appearance, but also for the usability and durability of buildings, for the protection of people and property, and for creating a comfortable indoor climate. More than that they have a huge impact on operating and embodied energy of buildings. To end up in a carbon neutral building we first of all have to extend the period in which the interior conditions can be kept comfortable without the need for mechanical systems. The solution is a holistic design approach with the goal to optimize the façade appearance and performance from operating and embodied energy. The most promising approach for that challenging task is based on five principles:

- Designing facades modularly with integrated and scalable functional groups. - Integrating HVAC- and solar-system-components into the façade.

- Consequent application of system technology for each of the different trades. - Proper use of cyber-physical systems within the entire lifecycle.

- Using the principles of a holistic parametric design process.

The objective of this paper is to give an overview of challenges and trends in advanced façade technology.

Keywords

operating energy, embodied energy, passive, active, cognitive, modular, system technology, smart tech

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1 INTRODUCTION

Across centuries, building forms and types have been adapted to local climatic conditions, based on the use of natural resources. Only in the 20th_{century did the advent of heating and air conditioning}

systems allow the design of building envelopes independently of the conditions and parameters of the local setting. However, this development came at a price. Not only are the initial and operating costs on the rise but the dependency on complex technology. The increasing need for energy and raw materials as well as the resulting CO2-emissions are alarming consequences.

In December 2015 a global climate change agreement that laid the groundwork for a low-carbon future was signed in Paris. In order to make that idea a reality, governments, companies and individuals have to work together. Buildings are directly responsible for approximately 40 % of the worldwide energy consumption. Because of their life expectancy mistakes we make today will lead in the long term to an economic, ecological and sociocultural burden. This is the main reason why almost worldwide there is a rising awareness of sustainability and why advanced concepts for “green” buildings are in fashion within the architectural society. Having said this we have to keep in mind that besides practical aspects we have to consider the regional culture of building (“Baukultur”) with its specific formal and symbolic aspects.

According to the target set by the Federal Government for the energy transformation (Energiewende) Germany’s building stock is to become “nearly climate-neutral” by 2050. A carbon neutral building is defined as one with significantly reduced energy consumption combined with the increased use of low carbon energy sources to meet the remaining demand (Carruthers & Casavant, 2013). Within this paper the definition of carbon neutral buildings includes the components operating and embodied energy as well as the resulting CO2-emissions. Façades are vital not only for the external appearance, but also for the usability and durability of buildings, for the protection of people and property, and for creating a comfortable indoor climate. Nevertheless we will have a focus on the role of façades to achieve a carbon neutral building stock.

2 INFLUENCE OF FACADES ON OPERATING ENERGY

Operating energy and CO2-emissions refer to the equipment for running the façade (e.g. electric drives) as well as for heating, ventilating, cooling and lighting of the building. An energy efficient façade - on the one hand - minimizes the operating energy - on the other hand - the size or even the necessity of HVAC-equipment. To end up in a carbon neutral building we first of all have to extend the period in which the interior conditions can be kept comfortable without the need for mechanical systems. It is important to point out, however, that this must not be at the expense of room comfort, which has an impact on well-being and productivity of people. Thus the importance of a comfortable temperature, fresh air and the use of daylight cannot be overestimated. Poor designs create

unacceptable comfort levels despite needing enormous amounts of energy. The starting point of a holistic optimization process is thoroughly analyzing the site. It has to include both environmental and climate factors in order to check the critical issues (negative forces) and potentials (positive forces) offered by the site that could be useful to control the indoor environmental conditions

(Ausiello & Raimondo, 2014). A key factor is having a building structure that is suitable for its location and its use, in conjunction with an appropriate façade (Daniels, 1995).

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The energy efficiency can be increased considerably if project-specific requirements are placed on room comfort, rather than just general measures, which may be over-stringent. Ideally, relevant comfort limits are defined separately for each building zone. It can be further optimized if the designer widens the “systemic boundaries”. For example, a weather-protecting enclosure between neighboring building parts may be designed as a large buffer zone, resulting in an atrium or mall-type space. Within tolerable limits their internal conditions are free floating, defined by the thermal behavior of the building. The internal surfaces of such spaces are relatively simple and do not require any particular attention in regards to wind loads or driving rain. Important nevertheless are the effects with regard to internal noise (“sound attenuation”) and thermal storage behavior (“thermal buffering”). Energy efficient buildings can be designed on basis of passive, active or cognitive concepts (Heusler, 2013).

2.1 PASSIVE CONCEPTS

Depending on where the building is located, it is affected by various environmental factors, namely noise, wind, precipitation, cold, heat and radiation from the sun. A passive façade seals off the interior from those external factors as far as possible. Contemporary mechanical systems ensure a comfortable interior environment. With advanced passive facades it is possible to even out long term differences between outside climatic influences and interior comfort conditions independent of the season. Short term variations for instance between day- and nighttime can be dampened and smoothed out as well. In regions with temperate climates, the most important functions of the building envelope consists, above all, of ensuring thermal insulation. This requires an overall optimization of frame, glazing and non-transparent areas of the facade. Thermal bridging within the component and where individual components are joined is also of significance. The better the quality of thermal insulation of a facade, the more important is a focus on thermal loss due to ventilation or infiltration. The overarching goal must be that uncontrolled ventilation due to gaps in the construction needs to be avoided. However, optimizing energy consumption must not end with heat loss. By using passive solar energy, the building itself acts as a solar collector. Transparent and translucent areas of the facade capture solar energy for space heating. In the case of buildings with high internal loads and large glass surfaces, solar radiation can occasionally cause overheating if no additional measures are considered. External shading systems reduce the solar radiation and the resulting thermal gains noticeable (Heusler, 2004). Daylighting systems can optimize interior lighting by evenly distributing the daylight entering the room (Heusler & Scholz, 1992).

2.2 ACTIVE CONCEPTS

In active building concepts dynamic façade components respond specifically to changing internal and external conditions (Heusler, 2013). The aim here is to minimize the use of mechanical systems, especially by means of natural ventilation, improved passive use of solar energy and daylight through operable windows, active sun-shading (Heusler, 2004) and movable daylighting systems (Heusler & Scholz, 1992). In comparison with twin-wall façades, considerably better thermal insulation results can be achieved by means of movable, temporary thermal insulation, especially if vacuum-technology is used as within the Schüco-2-Degree-Concept at BAU 2011 in Munich (see fig. 1). It is important to point out that the knowledge and behavior of users and/or operators of buildings, an aspect we may call “Operational Competence” becomes of increasing significance in active concepts. The most innovative building concept will inadvertently fail if it only performs in theory.

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FIG. 1 Active façade with temporary thermal insulation using sliding vacuum panels (white surface finish) as part of the Schüco-2-Degrees-Cconcept (Source: Schüco International KG)

According to my personal experience purely passive building concepts are only advantageous if the location, the height or the use of the building excludes natural ventilation, as well as solar energy and use of daylight for at least two-thirds of the year. In tall buildings natural ventilation through conventional windows and external solar shading installations is pushed to its limit by high wind loads.

2.3 COGNITIVE CONCEPTS

Adaptive building envelopes are able to interact with the environment and the user by reacting to external influences and adapting their behaviour and functionality accordingly. The idea for this principle first came up as Le Corbusiers “Mur Neutralisant and Respiration Exacte” within a proposal for „City of Refuge“ / Paris in 1929 (Diaz & Southall, 2015). In 1981 Mike Davies (Davies, 1998) picked up Le Corbusier`s idea and optimized it as his theoretical “polyvalent wall”. It would control the flow of energy from the exterior to the interior using extremely thin layers. The membrane would have the ability to absorb, reflect, filter, and transfer energies from the environment. According to Davis (Davies, 1998), it would continuously adapt and change to the surrounding conditions and act as a filter in both directions, interior and exterior. The “polyvalent wall” acts as a driving force for new façade technologies since that time (Ataman & Rogers, 2006) (Loonen, 2010). Together with Richard Rogers Mike Davis put parts of his concept into practice for the first time in the “Lloyds of London Redevelopment” Project / London finished in 1986.

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In many moderate climatic zones, optimum energy efficiency is provided by cognitive building concepts (Dascal & Dror, 2005). In relation to specific microclimatic conditions, their adaptive façades can modulate external signals. They are connected to mechanical-system components with dynamically adjustable functions through an intelligent building automation system. Adaptive components of the facade are capable of reacting to non-continuous, changing external and internal conditions that are in many instances predictable and can be calculated, such as the case with annual or diurnal swings in meteorological conditions (i.e., solar altitude angle) or the times of a building’s operation. However, non-predictable weather and operational aspects - such as variations in cloudiness and spontaneous presence of users - should be included by means of appropriate sensors or via the Internet through the weather forecast. Within the European research project COST TU 1403 “Adaptive Facades Network” scientists, engineers, architects and industry partners from 26 countries are sharing their knowledge, expertise, resources, and skills in the fields relevant to adaptive facades (Luible, et al., 2015).

Nowadays simulation tools allow for predicting the buildings free floating behavior in relation to varying external and internal conditions. They are the starting point of an anticipatory controlled, prioritized and coordinated operation of the façade’s individual components. It will purposively balance parameters such as its total energy transmittance and heat transmission and by this maximize “zero-energy-states”. The efficiency of passive nighttime cooling can be enhanced if lower temperatures are acceptable in the morning in not permanently used zones of the building. The upper mentioned buffer zones may be equipped with cognitive envelopes to provide a general thermal environment ranging in air temperatures between 15 and 30°C annually, largely independent of external weather conditions.

In the past there has been a gap between new technologies and their application into architecture. Recent developments in digital technologies and smart materials have created new opportunities and are suggesting significant changes in the way we design and build buildings (Attmann, 2012). A new architectural material class will merge digital and material technologies. Sensors and electronics will be embedded in architectural components such as glass. Cyber-physical systems (CPS) represent the next evolutionary step from existing embedded systems (acatech, 2011). The computational and physical processes are tightly interconnected and coordinated to work together effectively, often with humans in the loop. The potential of CPS to change every aspect of life is enormous. They will shift the reliance on human decision making into new, more strategic aspects and will increasingly rely on operationalizing human knowledge through computational intelligence (N.N., 2013). The basis is a system that can interact appropriately with humans and the physical world in dynamic environments and under unforeseen conditions. In combination with cognitive technologies CPS will have an enormous influence on architecture and the building industry.

3 INFLUENCE OF FACADES ON EMBODIED ENERGY

If buildings use nearly zero energy for operation, the ecological quality of a building is defined by its materials (Hildebrand, 2014). Therefor the second step to a carbon neutral building is taking into consideration the CO2-emissions associated with energy embodied in the building materials. There is carbon involved in the extraction of the resources that are used to create materials for facades as well as in the production and installation of facades. The optimization process has to consider the entire lifecycle, from design and construction, through operation, service and maintenance, updating and upgrading as well as demolition and recycling. Resource efficiency stimulates the minimization, material effectiveness the optimization of embodied energy over the life cycle phases of a building and its components. Truly material-effective facades incorporate the following factors:

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–

optimizing the materials used in their construction

–

minimizing the wastage of materials along the whole lifecycle

–

optimizing maintenance, servicing and modernization

–

increasing the recycling properties of components.

To achieve the lowest possible ecological impact, the architect first of all has to create a compact building with an efficient layout and optimized A/V ratio. The second step is integrating the end of life into the planning process (Hildebrand, 2014). The goal is minimizing the consumption of primary resources by means of a closed loop construction. There is a preference of re-using building components over recycling materials. In the end the challenge is that the old components do not fulfil contemporary functional requirements. Urban mining has to be taken into consideration. Reducing scrap and recycling production waste are representing the next steps. Other potential areas include minimizing wastage in the storage, packaging and transportation process.

Another topic is the intended life span. Every building and its components are subject to ageing. Careful and proper usage, regular cleaning, servicing and maintenance work can only slow the process of the materials ageing. Irrespective of this, however, a building and its fixtures and fittings may become obsolete if these no longer meet today’s comfort and quality requirements (“immaterial ageing”). The building structure is subject to less exchange cycles compared to the facade or even the building interior. Therefor disassembly and reassembly of building components need to be taken into consideration. In this context the importance of modular principles and system technology cannot be overestimated.

3.1 MODULAR PRINCIPLES

The modular principle is a design approach that subdivides a system (in our case a building) into smaller parts called modules. Nowadays the separation of a load bearing skeleton-construction and a non-loadbearing curtain wall is common in high-rise buildings. In many cases the principle goes one step further: The curtain wall is subdivided into unitized scalable modules. They can be developed and produced independently (most favorably in specialized factories) and used in different configurations (usually installed on site). Such modules comprise enclosed frames of façades including glass, panel, metal sheet and insulation, in extreme cases with natural stone and solar shading, sensors and motors. In the development of modules and sub-assemblies, the differences in ageing as well as the maintenance, servicing and modernization cycles of the individual components have to be taken into account.

The major advantage of unitized façades in contrast to stick-systems, is the high degree of automation and accuracy possible under controlled factory conditions. The result is reliable quality. The modules are transported in their entirety to site and fitted to consoles which were previously attached to and adjusted on the building`s structure. By this unplanned improvisation and wastage will be minimized. Reduced dependency on the weather provides a substantial basis for consistency of quality.

FIG. 2 The modular principle (Source: Schüco International KG)

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3.2 SYSTEM TECHNOLOGY

A good modular system is characterized by thoroughly optimized interfaces between adjacent modules. They are extremely important in the maintenance and demolition-process of building materials. It is possible to reduce the embodied energy of facades if their internal and external interfaces are based as far as possible on task-specific standards. System technology standardizes building components with identical or similar parts, and harmonizes the link between the

components (in terms of their dimensions and geometric interfaces). The application of this principle to the facade entails optimizing as many components as possible from an economic and ecological, as well as from an embedded energy point of view.

As there are fewer different construction types and parts, the design is less complex. In addition, components that are commercially and industrially (pre)fabricated as standard products are less complex than custom designed products. The more extensive and well thought-out the system and the more intelligently the planners and designers use it in adapting the design to fit the project specific requirements, the greater the chance of combining the system components to meet technical and design requirements in an efficient and individual way.

The wastage of materials can be considerably reduced if materials are re-used. If this is not possible, materials can be recycled preferentially. The choice of bonding technology and the connecting of materials will determine whether demolition results only in special waste that is uneconomical to recycle or in building materials that can be separated easily and cleanly.

4 INTEGRATION OF HVAC AND SOLAR COMPONENTS

INTO THE FAÇADE

As early as in 1999 SCHÜCO presented its CONCEPT façade at the BAU fair in Munich as a study based on the principles of integrated design and decentralized building plant components. Besides the automation and control of windows for natural ventilation, the integration of movable solar shading (with pivotable glass louvres), decentralized mechanical ventilation (with heat recovery and heat storage) and photovoltaic or solar thermal systems (including small decentralized adsorption chillers), has been realized using the principle of modularization. The CONCEPT facade harmonized all of the curtain wall’s components, including the HVAC and solar components as well as the control system, that offers the possibility of connecting facade components and the building plants components so that they can intercommunicate.

Since that time step by step ideas of the CONCEPT façade have been transferred into real products, not only at SCHÜCO. We are nowadays facing a large variety of mechanical, electric and electronic components as well as new materials within advanced facades. Different trades` competences are necessary for the successful solution of this cross-disciplinary challenge. In the current façade industry the principle of convergence represents the next evolutionary step towards value-added solutions for the building`s life cycle. Convergence is the merging of industries and the blurring of existing lines, within which single enterprises used to position themselves in the past.

4.1 INFLUENCE ON OPERATING ENERGY

In several projects de-centralized mechanical ventilation components have been integrated into the façade (Hartwig, Hellwig, Giertlová, Marghescu, & Ehlers, 2003). As they are equipped with regenerative heat exchangers the ventilation heat loss can be reduced. If they incorporate phase-change-materials (PCM), they are capable of balancing diurnal temperature fluctuations. If the capability to store thermal energy is great and, additionally, the local climate possesses the advantage of diurnal temperature swings, mechanical cooling systems may even become obsolete.

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If a building is optimized with regard to its energy efficiency, it is recommended – as the final step to achieve a carbon neutral building - that renewable energy sources be considered to compensate for the remaining energy consumption. In the case of facades, mainly two available active-solar energy sources are to be considered: electric and thermal.

The direct use of solar radiation for space heating and hot water consumption can be achieved with various available systems, which work according to various principles, such as air or water collectors or heat absorbers with heat pumps. Their performance can be increased with the addition of (probably decentralized) thermal storage systems. Especially for the building type of an office building, the generation of cooling energy with the help of thermal collectors and absorption chillers is of great interest (Khelifa, 1985) (Safarik, 2003). The principle is simple: in case of the highest cooling demand, the sun will provide the maximum intensity and potential for the cooling-process. This, of course, is an elegant balance between „supply and demand“.

Building-integrated photovoltaic systems (BIPVs) today have long passed the experimental phase. Thanks to system technology the problems of proper cable routing and electric connectors are solved in detail, and excellent systems are available.

FIG. 3 Photovoltaics and thermal collectors integrated into the building envelope; the Schüco-E²-Façade (Source: Schüco International KG)

4.2 INFLUENCE ON EMBODIED ENERGY

The CO2-emissions associated with energy embodied in the above mentioned components can be reduced by using modular principles and system technology. By designing facades with integrated and scalable functional groups for each of the different trades, even complex project specific solutions can be planned and executed more efficiently, flexible and with a higher quality. The basis for this advanced concept is the cooperation between the functional groups through optimized interfaces. Modular systems - with standardized functional principles - are favorable for that purpose. The modules can be developed and produced independently in specialized factories and installed on site by specialized installers. Within the modular concept the differences in ageing as well as the maintenance, servicing and innovation cycles of the individual components from the different trades have to be taken into account.

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In the end the application of the modular principle and system technology to the HVAC- and solar-system-components leads to an optimization regarding economic and ecological aspects as well as with regard to embedded energy. Extremely important (especially in terms of warranty) are the interfaces between the different trades modules. Standardized and optimized adapters or docking-stations seem to be a good solution for this complex task.

5 SMART TECH CONCEPTS

The basic question is whether a low tech or a high tech solution is the better one in terms of operating and embodied energy as well as CO2-emissions. From my personal point of view neither the low tech nor the high tech but the smart tech concept is the best one. It uses only as much technology as ultimately necessary. It follows the “lean-approach” to diminish or even eliminate the unnecessary and useless consumption of energy, materials, time and money (Daniels, 1998). Following the bioclimatic design strategy (Yeang, 1995) (Yeang, 1996), the aim is to minimize the use of mechanical systems by means of natural ventilation as well as the passive use of solar energy and daylight. The building and its facade have to be developed according to the project specific boundary conditions. Many mega cities (with high growth rates) are in regions with tropical climates. One solution for that specific climatic zone can be the passive building concept. The alternative is to return to the traditional cooling method of natural ventilation and to create building zones with different levels of comfort in accordance with the onion peeling principle. The core zone has to be sealed off from the surrounding buffer zones (airtight and well insulated). Court yards, atria, loggias and sky gardens can be part of those concepts. The outer layer should not be glass but a rigid, partially transparent solar shading installation that allows the permeation of air. Movable and in particular motor-driven components in such regions are only suited to buildings whose owners have a positive attitude to maintenance. Independently of the location an important point is not to focus on improving individual components, but to optimize the overall performance of the building structure, building envelope, interior walls, floors, ceilings, storage mass, technical fixtures and fittings, and building management technology. The optimum method for that highly complex task is using the principle of parametric design. It uses variables and algorithms to generate a hierarchy of mathematical and geometric relations. It serves the automated generation of geometries of architectural elements and physical characteristics of the components that change their properties based on formal relations. It is the shift from using CAD software as a drafting tool, to an efficient design tool - for the development of smart tech concepts. The actual challenge in the holistic design approach is to decouple the façade appearance and performance from operating and embodied energy and their CO2-emissions. By designing facades modularly with integrated and scalable functional groups (including minimized HVAC- and solar-system-components) and using system technology for each of the different trades seems to be a promising way. In combination with the proper use of cyber-physical systems it will have an enormous influence on architecture and the building industry.

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References

acatech. (2011). Cyber-Physical Systems: Driving force for innovation in mobility, health, energy and production.

Ataman, O., & Rogers, J. (2006). Toward New Wall Systems: Lighter, Stronger, Versatile. Proceedings of the 10th_{Iberoamerican}

Congress of Digital Graphics (pp. 248-253). Santiago de Chile, Chile: SIGraDi.

Attmann, O. (2012). Architecture as a Science - Integrating Macroelectronics Technology into Buildings. International Journal of Architecture, Engineering and Construction .

Ausiello, G., & Raimondo, M. (2014). Modulation performances in the building envelope: strategy and project. GBC Sustainable Building 14.

Carruthers, H., & Casavant, T. (2013). What is a Carbon Neutral Building? Vancouver, BC: Light House Sustainable Building Centre Society.

Daniels, K. (1995). The Technology of Ecological Building – Basic Principles and Measures, Examples and Ideas. Birkhäuser Verlag. Daniels, K. (1998). Low-Tech, Light Tech, High Tech: Bauen in der Informationsgesellschaft. Birkhäuser Verlag.

Dascal, M., & Dror, I. E. (2005). The impact of cognitive technologies: Towards a pragmatic approach. Retrieved from http:// cognitiveconsultantsinternational.com/Dror_CT_pragmatics_cognitive_technologies.pdf

Davies, M. (1998, February). A wall for all seasons. RIBA Journal.

Diaz, L., & Southall, R. (2015). Le Corbusier’s Cité de Refuge: historical & technological performance of the air exacte. Le Corbusier 50 years later, conference Valencia. Retrieved from http://dx.doi.org/10.4995/LC2015.2015.796.

Hartwig, H., Hellwig, R., Giertlová, Z., Marghescu, A., & Ehlers, M. (2003). Dezentrale Fassadenlüftungstechnik. Frankfurt am Main: Forschungsvereinigung für Luft- und Trocknungstechnik e.V. ( FLT).

Heusler, W. (2004). Sommerlicher Wärmeschutz – Glasmodifikationen und Additivsysteme. Innovative Fassaden II, VDI Berichte Nr. 1811. Düsseldorf: VDI Verlag GmbH.

Heusler, W. (2013). Bewegung in der Gebäudehülle? Gegenüberstellung passiver und aktiver Konzepte. In B. T. Weller, Glasbau 2013. Berlin: Ernst & Sohn Verlag .

Heusler, W., & Scholz, C. (1992). Neue Tageslichtsysteme – Ergebnisse einer experimentellen Untersuchung. HLH 43 Nr. 8. Hildebrand, L. (2014). Strategic investment of embodied energy during the architectural planning process. Dissertation TU Delft.

Delft.

Khelifa, N. (1985). Das Adsorptionspaar Silicagel-Wasserdampf, Anwendung als solares Klimatisierungssystem. Dissertation TU München.

Loonen, R. (2010). Overview of 100 climate adaptive building shells. Eindhoven: University of Technology. Retrieved from https:// pure.tue.nl/ws/files/15945980/Loonen2010_OverviewOf100ClimateAdaptiveBuildingShells.pdf

Luible, A., Overend, M., Aelenei, L., Knaack, U., Perino, M., & Wellershoff, F. (2015). Adaptive facade network - Europe. TU Delft Open for the COST Action 1403 adaptive facade network.

N.N. (2013, January). Strategic R&D Opportunities for 21st_{Century Cyber-Physical Systems – Connecting computer and information}

systems with the physical world. Retrieved from Report of the Steering Committee for foundation in Innovation for Cyber Physical Systems: http://www.nist.gov/el/upload/12-Cyber-Physical-Systems020113_final.pdf

Safarik, M. (2003). Solare Klimakälteerzeugung – Technologie, Erprobung und Simulation. Dissertation Universität Magdeburg. Yeang, K. (1995). Designing with Nature: The Ecological Basis for Architectural Design . New York: McGraw Hill, Inc.

Yeang, K. (1996). The Skyscraper: Bioclimatically considered. London: Academy Editions.

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Building Envelope as Heat Generator – The impact of Water-filled ETFE Cushion on Energy saving and Comfort

Building Envelope as

Heat Generator –

The impact of Water-filled

ETFE Cushion on Energy

saving and Comfort

Abolfazl Ganji Kheybari1_{, Jochen Lam}2

1 Transsolar Academy, Curiestraße 2, 70563 Stuttgart, +49 162 876 3731, fazel.ganji@gmail.com

2 Transsolar Climate Energietechnik GmbH, Curiestraße 2, 70563 Stuttgart, +49 711 67976-195, jlam@transsolar.com

Abstract

Inspired by the human skin and the blood circulation responding to heat and cold stress, Water-filled ETFE Cushion as a dynamic multi-functional building envelope is able to interact with different weather conditions by adjusting thermal and optical properties and improve the thermal and visual comfort and reduce energy demand consequently. At the same time this façade system as a semit-ransparent collector can gain solar energy.

This research evaluates the impact of using different configurations of Water-filled ETFE Cushion on Energy saving and Comfort by comparing the computational thermal and daylight simulation results with a typical office building in Dubai, Tehran and Stuttgart as base cases.

The results demonstrate the efficiency of water-filled ETFE cushion as dynamic system to provide thermal and visual comfort as well as reduce the energy demand and harvest solar radiation.

Keywords

Dynamic Envelope, Façade collector, Energy saving and Comfort, ETFE cushion, Radiance, TRNSYS

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1 INTRODUCTION

1.1 MULTI-FUNCTIONALITY OF FAÇADE AND SUSTAINABILITY

Increasing the transparency of architectural envelopes raises the energy demand of a building significantly in terms of heat gain and heat loss through large windows. Windows account for about 40% of total energy costs (U.S. Department of Energy, 2016) and are the major source of energy inefficiency in buildings.

Effective daylight utilization and smart use of passive solar gain are essential for achieving low-energy buildings with comfortable indoor conditions. Innovative multi-functional facade systems are able to provide responsively optimal conditions due to changing outdoor and indoor conditions and improve both the energy performance and comfort in a building by integrating solar collectors with the building’s form and its behavior concept. The building envelops have been forced to become real “active skins” with a very important energetic potential (Krippner, 2016) due to this urgent demand.

1.2 WATER FLOW GLAZING

The idea of using water as one of the best absorbers of solar energy (Otanicar, T.P., 2009) in glazing systems, has been evaluated in some projects under different names. The pioneer research is encapsulating water flow in a double glazed window to absorb the heat gain and reduce the electricity use for air conditioning system. This system as a transparent solar collector, can utilize absorbed heat for heating demands and domestic hot water (Chow Tin-tai et. al., 2011). The authors claimed two significant advantages of the system in comparison with air sealed double-glazing:

–

Higher heat capacity of water, thus more heat can be absorbed and consequently removed from the cavity. to avoid overheating of the cavity in multi-layer windows.

–

The removed heat which is absorbed in water can be utilized as a source of pre-heating in connection with active systems in building.

The other research project named “Fluid Glass” also developed the water filled glazing in which the solar transmittance of the glazing can be adjusted by dyeing the fluid which is circulated in chambers of the glazing (Stopper, 2013). The usage of the inner surface of the glazing as an active layer integrated into the HVAC system, increased the energy saving potential of the idea. The authors mentioned 20-30% of heating and cooling demand reduction for Munich, 70% for Madrid and 50-60% for Dubai (Ritter et. al., 2015).

1.3 MULTI-LAYER ETFE CUSHIONS

ETFE cushions have been largely used by architects since the 1980s as an alternative to glass because of their transparency, high thermal insulation properties, and energy and cost-efficient assembly and production processes (LeCuyer, 2008). Recent examples, such as the 2013 Enric Ruiz Geli’s Media-TIC building in Barcelona and Dolce Vita Tejo shopping-complex in Lisbon, showed the concerns about overheating and glare occurrence as a big issue for using ETFE cushions in sunny and hot climates.

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1.4 WATER-FILLED MULTI-LAYER ETFE CUSHIONS

The driving idea of using water bladder in a multilayer ETFE cushion is developing a dynamic shading and thermal component to interact with the variant environmental conditions. This interaction allows controlling the solar transmittance to get efficient solar heat gain during the winter and block solar heat gain during the summer while the sufficient daylight is providing. In addition, same as the Fluid glass, the large glazing area as an active heating and cooling surface can potentially improve the perception of comfort condition. The surface temperature of glazing closer to the temperature of other components of the building can also reduce the imbalance of long wave radiation in the space and raise the thermal comfort of the user (Ritter et. al., 2015).

FIG. 1 Total solar Irradiation and the potential of solar envelope to gain heat:. Based on the absorption coefficient of water with different thickness and ETFE foil transmission (Ganji & Lam, 2016).

Referring to Figure 1, it is noticeable that depending to the thickness of water, the light absorption in visible part of spectrum (380–700nm) in water layer is negligible (0.07% to 11.41%) but the solar absorption (250-2500nm) is significant (30.33% to 48.18%) in infrared range (Ganji & Lam, 2016). Therefore, regarding the different specular solar heat absorption and visible light transmission (Tvis) values corresponding to the thickness of water in this system, Water-filled ETFE cushion as a solution for semi-transparent façade element, can improve the heat gain potential of the glazing collector and reduce the energy demand by avoiding the overheating.

2 METHODOLOGY

2.1 CONCEPTUAL CONTROL SYSTEM: WATER AS BLOOD

Blood circulation and its variant velocity during cold and hot stresses are controlled by a feedback system in the hypothalamus; the temperature-regulating center of the brain (Lauster, 2009). When cold, in addition to keep the blood in internal organs of the body, by goose bump mechanism (or fluffing in birds) hairs are raised by small muscles to trap an air layer near the skin to reduce the convective heat loss. Inspired by the mammal’s body interaction to variant conditions, the dynamic solar envelope made of water-filled cushions in synergy with building active systems is capable of controlling the heat flux direction for saving or rejecting the heat (Figure 2).

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FIG. 2 Conceptual control system: the idea of building’s “Blood Circulation”, and integrated multi-functional façade components

2.2 MODELING

In this study, the geometry of a standard office room is modeled for daylight (in Radiance and Daysim) and thermal simulation (in Trnsys18) based on the technical standard of VDI 2078:2012-03, for three different climate conditions in Dubai, Tehran and Stuttgart for 2 people (17.50 m², 5.0 m length, 3.5 m width and 3.0 m height) (Figure 3). The south oriented window is 3.3 m by 2.8 m with 9.24 m² area. In this model, the U-value of 0.191 W/m²K is assumed for the external wall.

FIG. 3 The geometry of a standard office room and a section of simplified glazing system for main configuration with 1cm water

The glazing system for the base cases is a conventional double glazing window with U-value of 1.1 W/m²K and 60 % SHGC value. The frame fraction is assumed zero and a motorized external movable shading with 70% of shading fraction is active when irradiation values on the inner surface of the window is above 150W/m². The Artificial lighting gain of 10 W/m² is also added to the internal loads by controlling the 300 lux as minimum lux level with no dimming function.

Firstly, six different complex configurations with different shading effects have been generated in LBNL Window7.4 and combined with trnBSDF tool as a detailed window in a Pre-version of TRNSYS18; in order to evaluate the Energy saving performance of the proposed system. The amounts of annual energy demand [kWh/m².a] for heating, cooling and artificial light per square meter and thermal comfort for water-filled configurations have been compared with three base cases (Ganji & Lam, 2016). This study is focused on the impact of different facade configurations on thermal and visual comfort to evaluate the overall performance of system by comparing the energy saving potentials and the comfort conditions side by side.

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FIG. 4 six different definitions of glazing system, main configuration (number 1) is a multi-layer ETFE cushion with four foils with 0.25mm thickness

As shown in Figure 4, in this study the thickness of water layer is assumed as 1 cm for all six configurations. Configuration 0 (zero) is a conventional multi-layer ETFE cushion with 4 foils with 0.25mm thickness and three cavities and the main configuration (configuration 1) is a multi-layer ETFE cushion, where the middle cavity is filled with 1cm of pure water. The optical properties of systems for other four configurations (configurations 2 to 5) are adjusted by applying reflective coatings (HeatMirror77 and HeatMirror44 for configurations 2 and 3), and dyed water with pigment (1% and 2% of concentration for configurations 4 and 5).

2.3 WATER AS BLOOD AND SUMMER AND WINTER SCENARIOS

Based on the idea of “Water as Blood” and the solar absorption potential of water bladder, in summer, by gaining solar radiation inside water flow and allowing the visible light to transmit through the envelope, the system can effectively avoid the problem of overheating and consequently decrease cooling and electrical loads for artificial lighting due to benefiting from sufficient daylight (Figure 5). All these possible because The Qrej kWh [kWh/a] is the amount of solar heat, which is absorbed by the water bladder (as sunshade) and can be rejected to the earth or radiated to the cold sky overnight and represents cooling potential of the system during summer.

While the sufficient amount of visible light is transmitted to the space, during a winter day, collected heat can be used to support space heating as heat source for a radiant heating slab system or to provide hot water indirectly (Figure 6). During the cold night, the exterior air cavity plays the role of night insulation to reduce the heat loss. The Qcollect_kWh [kWh/a] is defined as a

representing parameter for passive solar gain potential of the system. This is the amount of useful solar heat gained during winter day in water bladder for different configurations. This amount of energy is simulated based on the average temperature of 35°C, which can be used for heating space during winter.